Ummm? Are you in bad health now?
I think the odds are closer to a relatively health conscious person making it to mid to late 80ties.
There is always the possibility that you will succumb earlier, but I think odds are in favor of living longer with reasonable measures taken.
I'll be 69 next birthday. I am a diabetic with type 2 controlled. If I'd been more astute about my weight earlier, I'd be in better shape. As it is, now I do quite a lot to possibly live longer, with quality of life. I try to eat responsibly, control my weight (I've done well here) and exercise. (Not doing as well here but it's constantly on my mind, even when I go shopping. I'll park out in the boonies and walk. Keeps my cars less door dinged also.)
So, it's really mostly up to you whether you make it to 2068 or 2070, barring bad luck or bad decisions. Now is the time to take charge of the rest of your life.
I'm heading for 2042 with no regrets. Regrets would only be a negative to my state of mind.
Oh, and now that I've reread and got your point (sometimes I skim too fast), nothing wrong with taking a contract that will expire earlier. There are lots of workarounds that we won't even know about until they happen.